AND THE ZOOLOGY OF CHINA 05 



and Eastern Europe. Here also two periods are observed. 

 lhe first— in the beginning of the summer, when the surface 

 water of the rice fields are free, under the sun's rays and the 

 water is not overshaded by rice stalks and manure ashes and 

 other things, which contribute to the growth in such water 

 of weeds and still more of algae. The second period comes 

 with the shading of the surface of the water by the rice stalks, 

 with chemical impoverishment of the water, and by a 

 gradual change of weeds and algae from one kind to another. 

 As observation shows, the life of the rice fields does not 

 always have its origin in the some manner, depending on the 

 quality and quantity of the manure, the age of the standing 

 water, the nearness of the fields to very dirty water, and 

 other causes. This can be seen when crossing the wide 

 river valley near villages or at some distance away. In the 

 cleanest water of rice fields more frequently were observed 

 — Salvinia natans L., MyriophyUum spicata L., Utricularia 

 vulgaris L., U. minor (?), Polygonum sp., Monochoria 

 vaginalis Presl., Isoetes sp., while in dirty fields were seen — 

 Wollfia arrhiza Wimm. Spirodela polyrrhiza Schleid., Lemna 

 minor L., Marsilia quadrifolia L. and Azolla sp., growing in 

 infinite numbers. Not less worthy of attention is the growth 

 of algae which play a great part in the life of these waters. 

 After an inundation in 1918 and the destruction of the young 

 rice plant the surface of the water became covered with an 

 alga — named "water-net" (Hydrodictyon utriculatum Both.) 

 This delicate alga has a bag-like form and consists of many 

 cells, forming a net with regular hexagonal cells. Firstly 

 the above mentioned cells were very small, but they quickly 

 increase in size and eventually all the algae get to the size 

 of the palm of the hand. It multiplies very quickly by the 

 moving zoospores in a sexless way. In the beginning the 

 alga was seen only on the surface of the slime under the 

 water, but in a short time it moves upward in a thick mass 

 and by strong exposure to the sun turns a grey-brown and 

 dies. During this time the water was very poor in organisms. 

 Here were seen some Flagellata, small diatoms; but with 

 the destruction in mass of the water-net" and its settling on 

 the bottom of the fields there began to appear — Salvinia 

 natans L., Lemna minor L., Spirodela polyrrhiza Schleid., 

 Marsilia quadripolia, Nitella sp., and on the bottom, .first 

 dark-greenish filaments and shortly after whole accumula- 

 tions of Spirogyra neglecta var. ternata. At that time the 

 shoots of Nitella and other under water plants and algae were 

 covered with thick layers of mucilaginous algae as Ruvularia 

 sp., diatoms — Gomphonema, Melosiravarians, Eunotia. Here 

 were examined — Pandorina morum, Eudorina elegans, various 

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